Modelling of Mg II lines in solar prominences

Abstract

Observations of the Mg II h and k lines in solar prominences with IRIS reveal a wide range of line shapes from simple non-reversed profiles to typical double-peaked reversed profiles with many other complex line shapes possible. The physical conditions responsible for this variety are not well understood. Our aim is to understand how physical conditions inside a prominence slab influence shapes and properties of emergent Mg II line profiles. We compute the spectrum of Mg II lines using a one-dimensional non-LTE radiative transfer code for two large grids of model atmospheres (isothermal isobaric, and with a transition region). The influence of the plasma parameters on the emergent spectrum is discussed in detail. Our results agree with previous studies. We present several dependencies between observables and prominence parameters which will help with interpretation of observations. A comparison with known limits of observed line parameters suggests that most observed prominences emitting in Mg II h and k lines are cold, low pressure, and optically thick structures. Our results indicate that there are good correlations between the Mg II k line intensities and the intensities of hydrogen lines, as well as the emission measure. One-dimensional non-LTE radiative transfer codes are well-suited to understand the main characteristics of the Mg II h and k line profiles in solar prominences, but more advanced codes will be necessary for detailed comparisons.

To appear in Astronomy & Astrophysics. Version 2 contains minor language editing

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• Reconstruction of a helical prominence in 3D from IRIS spectra and images
• First High-resolution Spectroscopic Observations of an Erupting Prominence Within a Coronal Mass Ejection by the Interface Region Imaging Spectrograph (IRIS)
• Two Solar Tornadoes Observed with the Interface Region Imaging Spectrograph
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Cited by in corpus (8)

• Solar prominence diagnostics from non-LTE modelling of Mgii h&k line profiles
• 1.5D NLTE spectral synthesis of a 3D filament/prominence simulation
• Spectro-imagery of an active tornado-like prominence: formation and evolution
• Mgii h&k fine structure prominence modelling and the consequences for observations
• Two-horn quiescent prominence observed in H-alpha and MgII h&k lines with THEMIS and IRIS
• A new view of the solar interface region from the Interface Region Imaging Spectrograph (IRIS)
• Evolution of the Ratio of Mg II Intensities During Solar Flares
• The diversity of spectral shapes of hydrogen Lyman lines and Mg II lines in a quiescent prominence